[PATCH] riscv: stacktrace: fix stack-out-of-bounds in walk_stackframe

[Matthew Bystrin]

Hi, Jiakai!

Thanks for your valid correction!

Jiakai Xu, May 14, 2026 at 13:07:
> -static inline int fp_is_valid(unsigned long fp, unsigned long sp)
> +static inline int fp_is_valid(unsigned long fp, unsigned long sp,
> +			      struct task_struct *task)
>  {
>  	unsigned long low, high;
>  
> +	if (!task)
> +		task = current;
> +

I would suggest to move this `if` into walk_stackframe() function in order to do
this only once before walking loop.

>  	low = sp + sizeof(struct stackframe);
> -	high = ALIGN(sp, THREAD_SIZE);
> +	high = (unsigned long)task_stack_page(task) + THREAD_SIZE;

Also after grepping `task_stack_page` I've noticed that pt_regs structure is
located at the end of stack. Maybe it is a good idea to adjust border even
"lower" to check that sp does not points inside pt_regs? (see task_pt_regs
macro)

>  	return !(fp < low || fp > high || fp & 0x07);
>  }

-- 
Best regards,
Matt